1. Field of the Invention
The present invention relates to a transflective type liquid crystal display, and more particularly to a single gap transflective type liquid crystal display having a high opening ratio.
2. Description of the Prior Art
Liquid crystal displays are classified into two types of liquid crystal display, namely a transmissive type liquid crystal display using a backlight as a light source and a reflective type liquid crystal display using a natural light as a light source. The transmissive type liquid crystal display can brightly display images under dark circumstances because of using the backlight as the light source, which has a disadvantage in that the backlight causes high power consumption of the transmissive type liquid crystal display. Meanwhile, the reflective type liquid crystal display uses natural light as the light source without using a backlight, resulting in low power consumption of the reflective type liquid crystal display. However, the reflective type liquid crystal display has a disadvantage in that it is impossible to use the reflective type liquid crystal display under dark circumstances.
Accordingly, a transflective type liquid crystal display has been proposed which is to compensate for disadvantages of the transmissive and reflective type liquid crystal displays. The transflective type liquid crystal display can be used in both transmissive and reflective manners, resulting in a relatively low power consumption and use under dark circumstance.
Such a transflective liquid crystal can be generally manufactured by processes of fabricating a lower array substrate (hereinafter, referred to as a lower substrate) including a thin transistor, a reflective electrode, and a transmissive electrode, fabricating an upper color filter substrate (hereinafter, referred to as an upper substrate) including a color filter and a common electrode, and forming a liquid crystal layer between the lower and upper substrates after attaching the two substrate to each other.
FIGS. 1 and 2 are views illustrating a transflective liquid crystal display according to a conventional art. Here, FIG. 1 is a sectional view showing the transflective liquid crystal display having a single cell gap, and FIG. 2 is a sectional view showing the transflective liquid crystal display having a dual cell gap.
Referring to FIGS. 1 and 2, the lower substrate 10 and the upper substrate 20 are disposed opposite each other. A liquid crystal layer 28 including a plurality of liquid crystal is interposed between the lower and upper substrates 10 and 20.
The lower substrate 10 includes a lower glass plate 11, a λ/4 phase-compensation plate 12 disposed on a surface of the lower glass plate 11, a reflective electrode 13 and a transmissive electrode 14 formed on the λ/4 phase-compensation plate 12, and a lower polarizing plate 15 attached on the other surface of the lower glass plate 11.
The upper substrate 20 includes an upper glass plate 21, a λ/4 phase-compensation plate 22 disposed on a surface of the upper glass plate 21, a color filter 23 including a black matrix (not shown) and formed on the λ/4 phase-compensation plate 22, and an upper polarizing plate 24 attached on the other surface of the upper glass plate 21.
In the transflective liquid crystal display having the single cell gap, as shown in FIG. 1, there is no step portion between the reflective region in which the reflective electrode 13 is placed and the transmissive region in which the transmissive electrode 14 is located, resulting in the same cell gap in the reflective region and the transmissive region.
On the other hand, in the transflective liquid crystal display having the dual cell gap, as shown in FIG. 2, there is a ½ cell gap between the reflective region in which the reflective electrode 13 is placed and the transmissive region in which the transmissive electrode 14 is located.
However, the conventional transflective liquid crystal display has following disadvantages.
First, as the transflective liquid crystal display is generally designed with reference to (based on) the reflective region, the reflective region has a phase retardation two times greater than that in the transmissive region of the transflective liquid crystal display having the single cell gap shown in FIG. 1. Therefore, a transmittance of the transmissive region is 50% less than that of the reflective region due to the phase difference between the transmissive and reflective regions, resulting in a transmittance difference between the regions.
In order to improve irregular transmittance between the reflective region and the transmissive region, the transflective type liquid crystal display must have a dual cell gap shown in FIG. 2. In the transflective type liquid crystal display having the dual cell gap, the cell gap of the reflective region is equal to half of the cell gap of the transmissive region. However, since a light path in the reflective region is two times longer than that in the transmissive region, the phase retardation in the reflective region is the same as that in the transmissive region, thereby causing the reflective and the transmissive regions to have an equal transmittance or similar transmittances.
The transflective liquid crystal display having the dual cell gap has a step portion between the transmissive and reflective regions, whereas the transflective liquid crystal display having the single cell gap has no step portion. This step portion makes a manufacture of the transflective liquid crystal display difficult, thereby causing a decrement in productivity of the transflective liquid crystal display.
Next, the conventional transflective liquid crystal display has the black matrix widely formed on the upper substrate in order to prevent leakage of light resulting form a misalignment of the lower and upper substrates. Thus, this causes the opening ratio to decrease.
In both of the transflective liquid crystal display having the single cell gap and the transflective liquid crystal display having the dual cell gap, further, light is transmitted twice through the color filter in the reflective region, rather than in the transmissive region, thereby causing a difference in reappearance capability of colors between the reflective region and the transmissive region.
Furthermore, both of the transflective liquid crystal display having the single cell gap and the transflective liquid crystal display having the dual cell gap have at least two phase compensating plates. The phase compensation plates cause an increased cost of the transflective liquid crystal displays.
In addition, the above-mentioned conventional transflective liquid crystal display has an uneven reflection electrode in order to increase reflexibility of the light introduced into the reflective region from outside, e.g. to evenly disperse the light reflected by the reflection electrode even though the light is introduced from all directions into the reflection electrode. However, since processes of forming prominence and depression on the reflection electrode are highly complicated, it is difficult to manufacture the uneven reflection electrode.